21372043921 has 2 divisors, whose sum is σ = 21372043922. Its totient is φ = 21372043920.

The previous prime is 21372043919. The next prime is 21372043991. The reversal of 21372043921 is 12934027312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21348424321 + 23619600 = 146111^2 + 4860^2 .

It is a cyclic number.

It is not a de Polignac number, because 21372043921 - 2¹ = 21372043919 is a prime.

It is a super-2 number, since 2×21372043921² (a number of 21 digits) contains 22 as substring.

Together with 21372043919, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21372043991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10686021960 + 10686021961.

It is an arithmetic number, because the mean of its divisors is an integer number (10686021961).

Almost surely, 2^21372043921 is an apocalyptic number.

It is an amenable number.

21372043921 is a deficient number, since it is larger than the sum of its proper divisors (1).

21372043921 is an equidigital number, since it uses as much as digits as its factorization.

21372043921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18144, while the sum is 34.

The spelling of 21372043921 in words is "twenty-one billion, three hundred seventy-two million, forty-three thousand, nine hundred twenty-one".